This invention relates to a method and apparatus for insulating an electrical component and, more particularly, to such method and apparatus for applying an expandable resilient insulating sleeve over a connector by first expanding the sleeve to receive the connector and thereafter releasing the sleeve to contract about the connector.
Electrical connectors such as female disconnects are typically insulated by either mechanically driving a sleeve of thermoplastic material, sized for an interference fit, over the connector or by placing the connector in an oversized sleeve of heat-shrinkable plastic material and applying heat until the sleeve has shrunk sufficiently to compressively hold the connector. A sleeve is applied via the first method only before the connector is crimped to a wire because, after crimping, only one end of the connector is accessible and the connector is difficult to hold firmly. It is relatively expensive to preinsulate connectors and crimping a preinsulated connector onto a wire has certain disadvantages in that a burr or piece of foreign matter on the crimping jaws could cause piercing of the sleeve. Also, a portion of the sleeve could be overstressed during crimping resulting in a nonuniformity of dielectric constant and requiring the sleeve to be relatively thick to insure provision of the necessary insulation characteristics.
Heat shrinkable tubing is typically applied after the connector has been joined to the wire. Heat shrinking the tubing is a relatively slow process; heat application times of ten seconds are not uncommon. Such tubing is also relatively expensive and care must be taken not to overheat the insulation on the wire when the sleeve is being applied to a connector already crimped onto a wire.
In another method of insulating a terminal, two insulating sleeve halves joined along one margin are folded to enclose the terminal. The other sides of the halves either have interlocking latch means or they are sonically welded together. This method includes many operations and is quite costly.
Apparatus has been proposed for stretching one end of a resilient insulating sleeve along parallel planes to provide an opening sufficiently large to receive a terminal. Such apparatus is part of a connector applying press and includes a pair of small fingers extending in the longitudinal direction of the sleeve. These fingers extend approximately to the midpoint of the sleeve and are movable to a spaced position wherein they extend one end portion of the sleeve. This method of mechanical expansion requires that the insulated wire to be terminated and to receive the sleeve have a smaller outside diameter than the inside diameter of the non-stretched portion of the sleeve and further requires the wire to be slid through the sleeve until the stripped end of the wire extends far past the fingers, a connector be positioned within the expanded portion of the sleeve. Thus, both ends of the sleeve must be accessible: the first end to slide the wire through the sleeve and the other end to terminate the wire and slide the connector back into the stretched portion of the sleeve. Reference may be made to U.S. Pat. Nos. 3,289,284 and 3,609,860.
Apparatus has also been proposed for inserting a generally cone shaped inner lining of ribbon film into a connector to serve as a guide for directing wires past protuberances extending inside the connector before the connector is deformed to mechanically engage the wires. The apron of the film extending outside the connector is folded back on itself and secured to the outside surface of the connector by using an annular elastic band. The connector is generally elliptical in cross section and as the minimum external width of the connector is less than the inside diameter of the band, the band is stretched only along parallel planes before being placed over the connector and the doubled back film apron. Reference may be made to U.S. Pat. No. 3,781,985.